Undocumented NetBT error 4321

[Douglas]

I have previously posted the problem below to this
newsgroup but so far no solution. I have found that
Event viewer shows the following error message, which
appears to correspond to the time that I lose the ability
to ping one the machines on my network:

NetBT error 4321

"The name "PARALLAX :1d" could not be registered on
the Interface with IP address 192.168.1.51. The machine
with the IP address 192.168.1.2 did not allow the name to
be claimed by this machine."

PARALLAX is the workgroup to which all the PCs on the
network belong. 192.168.1.51 is the machine that I am no
longer able to ping after this error. 192.168.1.2 is the
only machine on the network with a fixed IP address.

When I search on this error, I find:

We're sorry
There is no additional information about this issue in
the Error and Event Log Messages or Knowledge Base
databases at this time. You can use the links in the
Support area to determine whether any additional
information might be available elsewhere

Any ideas?

Problem previously described:

I have two Windows XP Pro machines networked via a